1. Field of the Invention
The present invention relates to a transport pipe for transporting solid materials such as sand, gravel or concrete. Such transport pipes are combined to form a pipeline such that each individual solid material transport pipe, in the following referred to as pipe, can be removed transverse to the length of the pipeline and replaced by a new pipe without having to pull the pipeline apart in its longitudinal direction. An exchange of pipes is necessary relatively often in such pipelines for solid material transport because the pipes, as a result of the abrasive nature of the transported material, are subjected to high wear loads at their inner side, especially at the transition area between adjacently arranged pipes.
2. Description of the Related Art
The aforementioned known pipes are, in general, provided at their ends with coupling collars which have circumferential grooves at their outer circumference. Clamping shells having a substantially U-shaped or trapezoidal cross-section are then placed into the grooves of two adjacently positioned coupling collars of two adjacent pipes. These clamping shells are pulled together by clamping or threading means so that in this manner two adjacently arranged pipes can be connected in a pull-resistant and pressure-resistant manner.
The connection of the coupling collars to a single-layer pipe section, hardened at its inner side, is realized such that the coupling collars are pushed by a certain amount over the ends of the pipe section and, subsequently, a fillet weld is produced between the outer surface of the ends and the adjacently arranged end faces of the coupling collar. For this purpose, the ends of the coupling collars facing the pipe section are provided with inner projections by which the coupling collars are correctly positioned at the pipe section.
The manufacture of such a pipe has been performed in the past such that the unhardened pipe sections are produced in overlength cut from a long pipe and then hardened. After hardening, the pipe sections are then cut to the desired length. Subsequently, the coupling collars are welded thereto. This not only results in a relatively high labor expenditure but also frequently in a change of the hardened microstructure of the pipe sections as a result of applying the welding seams. This change is a weak point within the inner wear-resistant area of a pipe in that exactly at the ends which are subjected to greater wear, in particular, when the pipes are angled relative to one another, additional wear will occur so that the pipes have to be removed already after a very short service life.
Furthermore, pipes are known which are provided with coupling collars that are directly connected as an axial extension of each pipe section and are welded to the axial ends of the pipe section by circumferential V-seams. Such pipes are generally hardened after the coupling collars have been welded to the pipe section, and this results in a relatively great expenditure due to the different wall thickness in the area of the pipe section and the coupling collars.